1. Field of the Invention
The present invention relates to a process for the manufacturing of a decorative thermosetting laminate with an abrasion and scratch resistant surface layer.
2. Description of the Related Art
Decorative thermosetting laminates are well known and used for instance as surface material for walls, cupboard doors, desktops, tabletops, for other furniture and as a flooring material.
Such laminates are often made of two to seven Kraft paper sheets impregnated with phenol-formaldehyde resin, a monochromatic or patterned decor paper sheet impregnated with melamine-formaldehyde resin and a fine so called overlay sheet of .alpha.-cellulose impregnated with melamine-formaldehyde resin.
The overlay sheet is intended to protect the decor paper sheet from abrasion. In certain cases the overlay sheet is omitted.
There are also laminates consisting of a base layer of particle board or fibre board provided with such a decor paper sheet and possible an overlay sheet. These sheets can be laminated towards the base layer under heat and pressure. If only a decor paper sheet is used then this can be glued towards the base layer.
The described laminates do have many good properties, it has however turned out that there is a great need of improving the abrasion resistance and the surface scratch resistance of laminates exposed to an extreme abrasion. This is especially the case for flooring laminates, but to a certain extent also for desktop and tabletop laminates.
According to the U.S. Pat. No. 4,940,503 the abrasion resistance of such laminates has successfully been improved. Then a paper web is impregnated with melamine-formaldehyde resin. At least one side of the web is coated with small dry and hard particles with an average particle size of about 1-80 .mu.m, evenly distributed over the wet resin surface on the web whereafter the resin is dried. The particle coated web, so called prepreg is thereafter possibly cut into sheets. At least one such sheet or web is placed as a surface layer on a base layer and bonded thereto. The hereby produced laminate will have a good abrasion resistance.
The hard particles used according to the prior art normally have an average particle size of around 50 .mu.m, which is an advantage from an abrasion point of view. It has, however turned out that the scratch resistance of laminates produced in the known way is not always satisfactory. Furthermore the press plates used during the laminating stage are scratched by the relatively big particles in the surface of the laminate. The press plates are very expensive and manufactured of a high quality steel. Intermediate layers of disposable aluminium foil are often used to protect these press plates which will affect the production cost.
There is a need to be able to produce an abrasion and scratch resistant decorative laminate and to avoid the above mentioned problems.